MFC 323631: Add an -a flag to getconf.

When -a is specified, the name and value of all system or path
configuration values is reported to standard output.

Sponsored by: Chelsio Communications

MFstable/11 r304949,r305226:

r304949:

MFC r303830,r304693,r304694,r304698:

r303830:

Remove vestigal references to __alpha__

Replace alpha reference in getconf(1) with amd64 [*]

PR: 211300 [*]

r304693:

Clean up trailing whitespace

r304694:

Add `MIN_HOLE_SIZE` pathconf(2) support to getconf

This allows shell programs to programmatically determine whether
or not a filesystem supports sparse files

r304698:

Add support for _PC_ACL_NFS4 as TRUSTEDBSD_ACL_NFS4

The TRUSTEDBSD prefix was chosen for consistency with the other
related `_PC_ACL*` prefixed variables.

r305226:

MFC r304809:

Add non-TRUSTEDBSD prefixed knobs for the _PC_ACL* and {CAP,INF,MAC}_PRESENT knobs

It's not necessarily intuitive that the variables to query contain TRUSTEDBSD
in the prefix. Add non-TRUSTEDBSD prefixed knobs for querying things like
"_PC_ACL_NFS4".

Relnotes: yes

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Warns fixes. Mainly unused headers/params/vars removal, but also
some malloc cleanup.

Add new 1003.1-2001/TC1/D6 parameters. (On final recirculation ballot now,
so this should be officially TC1 before the New Year.)

Add TrustedBSD pathconf parameters.

Add compilation support for -stable (to be merged momentarily).

Completely revamp the way getconf(1) works, for better adherence to the
intent of the Standard.

- Make getconf able to distinguish between configuration variables which
are entirely unknown and those which are merely not defined in the
compilation environment. The latter now get a more appropriate
"undefined\n" result rather than a diagnostic. This may not be
exactly right, but it's closer to the intent of the Standard than
the previous behavior.

- Support ``programming environments'' by validating that the environment
requested with the `-v' flag is the one-and-only execution environment.
(If more environments are supported for some platforms in the future,
multiple getconf(1) executables will be required, but a simple edit in
progenv.gperf will enable automatic support for it.) Document POSIX
standard programming environments.

- Add all of the 1003.1-2001 configuration variables. FreeBSD does not
support all of these (including some that are mandatory); getconf will
later be fixed to break the world should a required variable not be
defined.

As a result of all these changes, gperf is no longer adequate. Keep the
overall format and names of the files for now, to preserve revision history.
Use an awk script to process the .gperf files into C source, which does a
few things that gperf, as a more general tool, cannot do. The keyword
recognition function is no longer a perfect hash function.

This may obviate the need for gperf in the source tree.

- Add a small compile-time regression test to break the build if any of the
.gperf files declare conflicting token sets. (gperf itself would have done
this for the simple case of duplicate tokens in the same input file.)

Hello, getconf. This is a slight reinvention of the
wheel^H^H^H^H^HPOSIX.2 and X/Open utility, and rather
more complicated than necessary.